This invention relates to a method of softening fabrics during the rinse cycle of a typical wash process.
It has long been recognized that certain chemical compounds have the capability of imparting softness to textile fabrics. These compounds, which are known generally as "softening agents," "fabric softeners," or "softeners," have been used in the laundry to soften a finished fabric, thereby making the fabric smooth, pliable and fluffy to handle. In addition to the quality of softness, the fabrics frequently have a reduced tendency to static cling and are easier to iron.
A basic distinction can be made between a rinse cycle softener and a wash cycle softener. A typical wash cycle fabric softener usually constitutes solid particles of a quaternary ammonium compound and is mixed with a powder laundry detergent or added at the same time as the laundry detergent, usually before initiation of the wash cycle of the washing machine. Such a composition is convenient since it does not require a dispenser on the washing machine and the composition can be packaged in cheaper, more biodegradable, packages. However, wash-added softeners tend to be less effective than rinse-added softener compositions.
On the other hand, a rinse cycle softener is usually a liquid dispersion which is added to the rinse liquor during the rinse cycle. These liquid dispersions can be manufactured as such or can be formed by adding water to solid particulate softener compositions. A liquid product containing a small particle size dispersion/emulsion tends to more effectively cover the laundry fabrics. Although solid particulate fabric softeners can be added directly to, e.g., rinse liquor to form a dilute treatment bath for fabrics, the solid compositions are usually more effective when an aqueous concentrate is formed prior to addition to the rinse cycle. At low water temperatures, it can take up to fifteen minutes to form the desired, more effective, small particle size emulsion/dispersion. Fifteen minutes is typically longer than the rinse cycle in an ordinary automatic laundry machine. The present invention provides a way to obtain both the advantages of better efficacy of a liquid rinse-added softener composition and of packaging benefits of a solid softener composition while eliminating the steps needed to form an intermediate aqueous concentrate.
The softening agents which are usually employed in compositions intended for use by the individual consumer are cationic surfactant compounds. Historically, these were quaternary ammonium compounds having at least two long alkyl chains, for example, distearyl dimethyl ammonium chloride. The positive charge on the softening compound encourages its deposition onto the fabric substrate, the surface of which is usually negatively charged.
Although the above-mentioned cationic compounds are highly effective softeners when applied in a rinse solution, it is difficult to supply the traditional cationic softeners in a granular form which will readily disperse to form concentrated, finely divided, aqueous emulsions/dispersions having a concentration of from about 5% to about 30% of softener active. Cationic granule compounds having long alkyl chains tend to form highly viscous/non-dispersible phases rather than dispersions when added to water. However, by mixing certain granular nonionic softeners, or mixtures of nonionic softeners or cationics, with tap water, the consumer can form aqueous concentrated emulsions/dispersions of the type used by individual consumers. These compositions provide excellent deposition onto the fabric surface from dilute aqueous solution. The compositions are sold in granular form and used by the consumer to form typical aqueous, liquid, rinse-added fabric softener compositions of the general type disclosed in U.S. Pat. Nos.: 4,128,484, Barford and Benjamin, for Fabric Softening Compositions, issued Dec. 5, 1978; and U.S. Pat. No. 4,126,562, Golfinet and Leclercq, for Textile Treatment Compositions, issued Nov. 21, 1978; said patents being incorporated herein by reference.
Granular compositions and method of utilizing them provide a large environmental advantage versus existing liquid products since the granular products can be packaged in cardboard cartons that are essentially biodegradable rather than in plastic bottles which are more slowly degraded.